package com.fzn1.day02.double_;

import com.fzn1.day02.AbstractList;

/**
 * @program: DataStructure
 * 描述：  链表的实现  双向链表
 * @author: fzn
 * @create: 2022-11-12 17:12
 **/
public class DoubleLinkedList<E> extends AbstractList<E> {
    private Node<E> first;
    private Node<E> last;

    private static class Node<E> {
        E element;
        Node<E> prev;
        Node<E> next;

        public Node(E element, Node<E> prev, Node<E> next) {
            this.element = element;
            this.prev = prev;
            this.next = next;
        }
    }


    @Override
    public void clear() {
        size = 0;
        first = null;
        last = null;
    }

    @Override
    public E get(int index) {
        return node(index).element;
    }

    @Override
    public E set(int index, E element) {
        Node<E> node = node(index);
        E old = node.element;
        node.element = element;
        return old;
    }

    @Override
    public void add(int index, E element) {
        rangeCheckForAdd(index);
        if (index == size){
            Node<E> oldLast = last;
            last = new Node<>(element, oldLast, null);
            if (oldLast == null) { // 这是链表添加的第一个元素
                first = last;
            } else {
                oldLast.next = last;
            }
        }else{
            Node<E> next = node(index);
            Node<E> prev = next.prev;
            Node<E> node = new Node<>(element, prev, next);
            next.prev = node;
            if (prev == null) { // index == 0
                first = node;
            } else {
                prev.next = node;
            }
        }
        size++;
    }

    @Override
    public E remove(int index) {
        rangeCheck(index);
        Node<E> node = node(index);
        Node<E> prev = node.prev;
        Node<E> next = node.next;

        if (prev == null){
            // index == 0
            first = next;
        }else {
            prev.next = next;
        }

        if (next == null){
            // index == size -1
            last = prev;
        }else {
            next.prev = prev;
        }

        size--;
        return node.element;
    }

    @Override
    public int indexOf(E element) {
        Node<E> node = first;
        if (element == null){
            for (int i = 0; i < size; i++) {
                if (node.element == null) return i;
                node = node.next;
            }
        }else {
            for (int i = 0; i < size; i++) {
                if (element.equals(node.element)) return i;
                node = node.next;
            }
        }
        // 没找到
        return ELEMENT_NOT_FOUND;
    }

    /**
     * 获取index位置对应的节点对象
     * @param index 下标
     * @return
     */
    private Node<E> node(int index){
        rangeCheck(index);

        if (index < (size >> 1)){
            // 左边
            Node<E> node = first;
            for (int i = 0; i < index; i++) {
                node = node.next;
            }
            return node;
        }else {
            // 右边
            Node<E> node = last;
            for (int i = size -1; i > index; i--) {
                node = node.prev;
            }
            return node;
        }
    }
    @Override
    public String toString() {
        StringBuilder string = new StringBuilder();
        string.append("size=").append(size).append(", [");
        Node<E> node = first;
        for (int i = 0; i < size; i++) {
            if (i != 0) {
                string.append(", ");
            }

            string.append(node.element);

            node = node.next;
        }
        string.append("]");
//      第二种遍历方式
//		Node<E> node1 = first;
//		while (node1 != null) {
//
//			node1 = node1.next;
//		}
        return string.toString();
    }
}